Some sealing systems used for sealing the annular space between the rings of a bearing assembly include a pair of sealing shields which are inserted in coaxial combination between the rings of the bearings, one of the shields being attached to the outer ring and the other to the inner ring. One of the shields is usually provided with one or more sealing lips capable of interacting either radially or axially with the other shield or directly with a surface of the opposing ring in cases where the sealing system includes only a single shield. The shield attached to one of the rings must be capable of frictionally engaging with a seating surface in the ring itself. For this purpose the shields were usually provided with anchoring means which comprises either a sleeve shaped portion of an internal metallic reinforcing member of the shield or an elastomeric sleeve which can be elastically compressed radially usually produced as a unit with the sealing lips capable of engaging with interference with the seat so as to remain interposed between the seat and sleeve portion of the reinforcing member of the shield. In the first instance, the securing occurs by means of direct interference fit between the seat and the sleeve portion of the reinforcing element of the sealing shield. Of course, in order to achieve a friction fit, the housing seat on the shield has to be made to very high precision within predetermined controlled restricted tolerances which experience has shown causes a number of design difficulties. Moreover, a press or interference fit is highly subject to dimensional changes resulting from differential thermal expansion which may occur during use in the coupled parts to the extent that in some severe cases, uncoupling can result with consequent detachment of the sealing shield from the bearing. This breakdown, of course, runs the risk of contaminants entering the bearing space and causing premature failure of the bearing.
In the second instance where the resilient sealing element is elastically compressed, the dangers of high tolerances are not present with the serious attendant consequences nor does the housing seat of the shield need to be worked with excessive precision since interposition of a compressible layer of rubber between the seat and the reinforcing element ensures that any inaccuracies in the construction of the seat and any thermal expansion are compensated for or absorbed. It has been found, however, that this type of joint presents other disadvantages and drawbacks. For example, it does not ensure precise correct axial positioning of the shield in the seat. More specifically, as the elastomeric sleeve deforms radially it also deforms axially and thus, presents a certain difficulty of seating or inserting the same in the seat. Consequently, this type of coupling can cause a decrease or even loss of the sealing action against external contaminants such as water and dust and loss of the internal lubricating grease of the bearing, especially in seals fitted with axial sealing lips.